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fact,afinitenumberofstraightlinescalculatedwiththemethodcanbefound
onlyandtakenasanapproximatemodelofthewarpedsurface,Fig.2-2.
Definition11
Alineofstrictionofawarpedsurfaceissuchaline,whosecurvaturesare
thebiggestonesfromalllinesintersectingallrulingsofthewarpedsurface
atthesametime.Thereforethelineofstrictioncanmodelacontractionof
eachshellsheeting.Themoreaccuratedefinitionispresentedinnextpart
ofthemonograph,seeChapter4.
Definition12
Acentralsectorofawarpedsurfaceofasectorofthewarpedsurface
whoserulingsareintersectedintheirmiddlepointsbythelineofstriction.
Theabovestraightlinesareregardedaschosenrulingsoftheshellsector.
Theserulingsareevaluatediterativelyasfollows,Fig.2-2.Ifthelinet
0
is
adoptedastheborderrulingforboththesectormodellingtheentireshell
sheetingandthesector
Ω
1
=<E
0
F
0
E
1
F
1
>modellingthefirstshellfold,thenthe
nextrulingt
1
limiting
Ω
1
hastobefoundatthefirststeep.Sovaluesofchosen
parametersdescribingthemutualpositionofthelinest
0
andt
1
arecalculatedso
thattheywouldlimitthecentralsector
Ω
1
ofarighthyperbolicparaboloid
correspondingtotheneutralsurfaceofthefirstfold[91].
Fig.2-2.Ondeterminingrulingst
warpedsurfaces
sheetingsonthebasisofthepara-
meters
cutting
α
,andloftwistingandoblique
ω
i
modellingshell
i
of
Inananalogousway,therulingt
i
modellinglongitudinalborderofthei
shellfoldattheisteepisfounded.Asaresult,theadjacentrulingst
i-1
andt
i
oughttolimitthecentralsector
Ω
i
ofarighthyperbolicparaboloid
ω
i
.The
model
Ω
ofthewholeshellsheetingisasumofall
Ω
i
.
Oneshouldtakecareofthefactthattheaccuracyofmodellingdependson
thetypeofparametersdescribingtheshapeoftheneutralsurfaceofashell
